1. Field of the Invention
The present invention generally relates to facial image processing techniques, and more specifically, an improved facial image processing method and apparatus for generating feature coordinate information corresponding to characteristic parts of a facial image useful in facial morphing, identification or blending operations.
2. Description of the Related Art
To merge two facial images, it is first necessary to extract the eyes, eyebrows, mouth, facial contours, and other facial features, calculate the coordinate data of the representative contour points forming the contours of each of the extracted features based on the extracted image data, and then transfer the calculated coordinate data to the image-merging processor in order to match a wire frame model of the facial shape to the actual facial image.
One facial feature extraction method commonly used detects the image edges based on the coordinate data and black/white density data of the input image data, and digitizes the image edges to extract the facial features. With this method, however, much noise is introduced into the digital image during processing, and processing of images rich in color information is limited. To resolve these problems, recently developed methods attempt to distinguish and extract the facial features using the color information contained in the image.
One such method follows a predetermined program to process and extract the facial features based on the coordinate and color data of the input image data. This method first stores the input image data to an image data memory, and then extract the facial features in a predetermined sequence, e.g., the mouth (i.e., lips) first, followed by the eyes, the eyebrows, and other facial parts, according to a predefined program. To extract the mouth, for example, the complete facial image data is queried to locate the image area using the YIQ color system, where the Q component, which expresses lip color, exceeds a certain threshold value. This area is extracted as the mouth area, which is then processed to obtain and output the coordinate data for the representative contour points forming the contour of the mouth and circumscribing lips. The coordinate data for the eyes and eyebrows is processed in the same manner to extract the respective areas and obtain the corresponding coordinate data.
As described above, these refined color techniques follow a predefined program to extract the facial feature areas from the complete image data, and to obtain the coordinate values for the extracted feature areas. In the mouth extraction process, for example, the collection of image areas in which the Q component exceeds a known threshold value is determined to be the mouth, and the mouth area is thus extracted based on the value of the Q components. However, when there is a Q component (red) area in the background of the facial image exceeding a predetermined saturation or level size, or when there is a red pattern exceeding a predetermined level in the subject's clothing, these areas may be mistakenly determined to be the area of a mouth. Naturally, this results in an inaccurate feature characterization of the input facial image. Significant processing time is also required to extract plural facial features, including the eyes, eyebrows, and mouth, from the complete facial image data, particularly in 16 bit high color or 24 bit true color applications.